1. Field of the Invention
The present disclosure relates to an apparatus and method for diagnosing malfunction of a high voltage relay device.
2. Background of the Invention
Electric vehicles and hybrid electric vehicles (HEV) obtain driving energy by rotating a motor with electricity accumulated in a battery. Since vehicles do not obtain energy by burning fossil fuel like existing vehicles, an exhaust gas can be reduced.
Driving force of an electric vehicle using a motor is transmitted to a wheel through a transmission. Unlike engines, a torque-speed maximum capability curve of a motor is continuous according to speeds, and thus, the motor has a single uniform fixed reduction gear ratio, and an inverter should control the motor at a high speed (in general, at 0 to 12,000 rpm).
In general, as a control power source of an inverter included in an electric vehicle, a 12V lead storage battery like that of an engine vehicle is used, but a voltage of a battery input to the inverter is a high voltage ranging from DC 200V to 400V.
Here, as illustrated in FIG. 1, in order to protect the battery having a high voltage, a relay unit 3 is connected in series between the battery and the inverter. In this case, the relay unit 3 may include one or more relays 31 and 32 by which the battery 1 and the inverter 2 are connected in series in each electrode.
Since the relays 31 and 32 are connected to the battery 1 having a high voltage so as to be driven, when a contact of the relays 31 and 32 is melting-bonded (hereinafter, relays 31 and 32 may also be used together with “high voltage relays”), a high voltage may be unintentionally applied to a system.
In order to solve the problem, Korean Patent Laid Open Publication No. 10-2013-0079843 discloses an apparatus for determining contacts of relays 31 and 32 are melting-bonded.
FIG. 2 is a circuit diagram of the related art apparatus for determining whether contacts of relays are melting-bonded.
As illustrated in FIG. 2, in the related art apparatus for determining whether contacts of relays are melting-bonded, when the relay 31 having a positive (+) polarity is melting-bonded, a voltage supplied from a high voltage battery is dropped through a resistor R1 and a first LED 41 is turned through a first photocoupler PC1. Conversely, when the relay 32 having a negative (−) polarity is melting-bonded, a voltage supplied from the battery having a high voltage is dropped through a resistor R5 and a second LED 42 is turned on through a second photocoupler PC2.
In this manner, the related art apparatus for determining whether contacts of relays are melting-bonded is advantageous in that a user can determine whether relays 31 and 32 of the electrodes are melting-bonded with naked eyes. However, whether the a contact of the high voltage relays 31 and 32 are melting-bonded is determined by using a current flowing in the circuits including various resistors R1 to R8 and the photocouplers PC1 and PC2, additional circuits and components are required.
In addition, due to the additional components, the related art apparatus for determining whether a contact of a relay is melting-bonded cannot reduce a size of a product to be designed and economic efficiency thereof is degraded.
Thus, a technique for solving the foregoing problem is urgently required.